I'm a grad student attempting to put together a reactive transport model in X1t. The goal is to construct a 2D reactive transport model to simulate groundwater chemical evolution in a substrate in my study area. My supervisor recommended starting in React and then working my way into X1t and then X2t, when I can get the previous simulations to run and follow the chemical trends I'm after.
My model includes clays, feldspars, carbonates, chlorite, and pyrite. I have XRD results to support wt% values for mineral species, and I'm using a series of kinetic reaction equations composed by my supervisor (which he gathered from reputable research). I got the model to run and follow the ion trends I have for 11 groundwater samples oriented along a flow path, using React. Now, I'm attempting to put together a 1D reactive transport model with the same setup.
For my initial solution, I'm using a mixture of the 11 samples I have (seems like an okay idea), and I'm flushing into the model a groundwater sample that represents a relatively fresh (low TDS) groundwater sample from elsewhere in my dataset.
I got the model to run without pyrite with some okay results. My issue is that I can't get the model to run if I include kinetic pyrite (0.03 wt%). I think it's because I'm not starting with good initial redox conditions and the model can't converge because oxygen fugacity is shooting off somewhere, but I'm not sure. Inevitably X1t crashes, unless I start with an initial oxygen partial pressure of approximately 2 atm! I guess my foremost question is how you recommend setting initial redox conditions. The aquifer I'm attempting to simulate is overlain by glaciolacustrine sediments, often tens of metres thick, so dissolved oxygen content is low. But, the lower of a value I use for initial oxygen fugacity, the quicker the model crashes.
I can get the model to run with "simple" pyrite, but I'm not sure if it is logical to keep adding pyrite at every step of the simulation.
One other thing I'm wondering about is how to plot saturation index plots in Gtplot from data in GSS. This seems like a trivial task, and I've put together dozens of scatter plots in Gtplot, but I can't get the same values I have in my GSS spreadsheet to plot in Gtplot. I have Log(Q/K) values in GSS that hover around saturation with respect to calcite, but when I plot them in Gtplot, no matter what style of axes I use, it shows SI values up to 10.
Attached is my X1t file, GSS spreadsheet of the samples oriented along the east-west flow path I'm trying to simulate, and I'll include a picture of the trends I'm trying to simulate. I've been at this for a few weeks, so any help would be greatly appreciated.
Reactive transport model 1D.x1t
Groundbirch PV samples.gss